Iron has been proposed to contribute to atherogenesis in humans by facilitating the oxidation of lipoproteins. This observational study will evaluate the association between frequency of blood donation - expected to be associated with relatively reduced body iron stores in frequent donors - and carotid atherosclerosis. The primary outcome variable will be whether the presence and extent of asymptomatic carotid atherosclerosis (as measured by ultrasound) is greater in infrequent (less than or equal to 1 donation/ year greater than or equal to 5 years) vs. frequent (greater than or equal to 4 donations/year greater than or equal to 5 years) blood donors. Body iron stores, lipid and hemostatic parameters, nitric oxide formation, inflammatory parameters, and markers of vascular oxidative stress will be analyzed as secondary outcome measures. Laboratory analysis and ultrasound testing will be performed blinded to the patient's phlebotomy and iron status. Sixty frequent (n = 40 males > 40 y/o, n = 20 females> 50 y/o) and 60 infrequent (n = 40 males > 40 y/o, n = 20 females > 50 y/o) blood donors will be recruited for this study from the Department of Transfusion Medicine, W.G. Magnuson Clinical Center. All donors will be assessed for study eligibility and cardiovascular risks during the screening visit. The presence of atherosclerotic lesions by carotid ultrasound and secondary outcome parameters will be assessed during a second visit.